Sleep Tracking on Apple Watch Series 7

I recently moved from Fitbit to Apple Watch. My Fitbit (Charge 3, no Premium) used to give me good insights on my sleep for e.g. REM, Deep, Light etc. Now, I understand AW does not give that level of data and that's fine.

My issues are that

• AW does NOT track sleep outside of a 'Sleep Schedule'
• When I do set up a Sleep Schedule, it ends my sleep at the time of my 'Wake Up' alarm. If I continue sleeping for an hour or so, it does NOT record that in my sleep.

All I need is for it to track the entire duration of my sleep. Surely it should be able to work out from my heart rate that I'm still sleeping, and not just end it at a pre-determined time? My Fitbit Charge 3 HR from 5 years old does that!

Is there any way to overcome this / am I doing something wrong?